Nancy Birtwhistle: She took a controversial shortcut on last night's Great British Bake Off

Great British Bake Off contestants are supposed to pride themselves on home-spun skills and recipes handed down the generations.

Now one of them has ditched tradition – in favour of the microwave.

Judges Mary Berry and Paul Hollywood were visibly shocked when grandmother Nancy Birtwhistle, 60, popped her dough in for a five-minute blitz at ten per cent power.

The idea behind Mrs Birtwhistle’s shortcut was to help the enriched sweet dough for her Lincolnshire plum bread rise faster, thereby stealing a march on her fellow competitors.

But baking experts also expressed dismay at the trick, saying microwaves have no place in any self-respecting baker’s kitchen.

Contestants on last night’s quarter-final were given only two-and-a-half hours to produce a perfect loaf, which Mrs Birtwhistle’s rivals complained was barely enough time to prove and cook their dough.

On hearing about the mircrowave quick-fix, Miss Berry turned indignantly to her fellow judge and said: ‘You never use a microwave do you?’

Hollywood said he did not, adding: ‘It destroys the protein structure, because you force in heat. It tends to break down, so it can destabilise the dough.’

Baking experts also criticised Mrs Birtwhistle.

Mike Holling, executive director of the Craft Bakers Association, said: ‘All it will have done is cook the dough while it is rising, instead of allowing it to rise at its own pace. You can’t rush these things. I never thought I’d see a microwave on Bake Off.’

Mrs Birtwhistle, from Barton-upon-Humber in Lincolnshire, admitted she was ‘a bit scared’ that her plan would backfire.

She added: ‘This could be my death knell. It should be all right. It’s been all right when I’ve tried it.’

Thanks to the extra heat provided by the microwave, her dough rose to an impressive size. However, Hollywood was unconvinced.